1. Field of the Invention
In general, the present invention relates to a shift control method for an electric-power-assist transmission. In particular, the present invention relates to a shift control method wherein a gear shift as well as the operations to put the main clutch in an engaged or disengaged state are carried out electrically. More specifically, the present invention relates to a shift control method whereby the main clutch is put back in an engaged state after being released from an engaged state by rotation of the shift spindle from a first rotational position to a second rotational position, with a rotational speed of the shift spindle changed from a first speed to a second speed lower than the first speed with a predetermined timing.
2. Description of the Background Art
In the conventional transmission, a gear shift is carried out by operating both a clutch pedal (or a clutch lever) and a shift-change lever. On the other hand, in an electric-power-assist transmission disclosed in Japanese Patent Laid-open No. Hei 5-39865, a gear shift is carried out electrically by a motor. In the conventional technologies described above, a shift drum is intermittently rotated in both directions by a driving motor so as to actuate a desired shift fork in a gearshift-change operation. On the other hand, it is possible to put the main clutch in an engaged or disengaged state also by using a motor as well.
In such a case, when thinking of the conventional manual transmission, only by repeating the shift-change operation can the shift change be eventually completed even if the gear is not shifted smoothly. In addition, whether or not the clutch can be put in an engaged state smoothly after the shift change much depends on the operation of the clutch carried out by the driver.
As described above, in the conventional manual transmission, most of poor operability as evidenced by whether or not a shift change can be completed without repeating the shift-change operation or whether or not the clutch can be put in an engaged state smoothly-much depends on how the operation is carried out by the driver. In other words, the driver""s learning effects allow good operability to be obtained.
By driving both the clutch and the shift-change lever by means a motor, on the other hand, elements dependent on the operation carried out by the driver do not exist any more. Thus, in a state where a gear shift is impossible, if the clutch is not put in an engaged state smoothly or not in accordance with the driver""s intention, it is quite within the bounds of possibility that the driver feels a sense of incompatibility.
When putting back the clutch in an engaged state after being released from an engaged state, for example, it is desirable to put the clutch in an engaged state slowly in order to reduce the magnitude of a generated shift shock. On the other hand, the speed of a shift change is dependent on the engagement speed of the clutch. It is thus necessary to put the clutch in an engaged state quickly in order to implement a fast shift change.
It is thus an object of the present invention to solve the problems described above by providing a shift control method to be adopted in an electric-power-assist transmission offering good operability wherein the time it takes to put the main clutch in an engaged state can be shortened and the magnitude of a generated shift shock can also be decreased as well.
In order to achieve the object described above, the present invention provides a shift control method to be main adopted in an electric-power-assist transmission wherein a clutch is put in an engaged or disengaged state in a manner interlocked with the rotation of a shift spindle rotated by a driving motor. The shift control method is characterized in that the clutch is put back in an engaged state after being released from an engaged state by rotation of the shift spindle with a rotational speed thereof changed from a high speed to a low speed with predetermined timing.
According to the configuration described above, in an operating zone having nothing to do with a shift shock, the clutch is driven at a high speed but, in an operating zone where the clutch is about to be put in an engaged state, the clutch is driven at a low speed. As a result, the time it takes to put the main clutch in an engaged state can be shortened and, at the same time, the magnitude of a generated shift shock can also be decreased as well.
Further scope of applicability of the present invention will become apparent from the detailed description given hereinafter. However, it should be understood that the detailed description and specific examples, while indicating preferred embodiments of the invention, are given by way of illustration only, since various changes and modifications within the spirit and scope of the invention will become apparent to those skilled in the art from this detailed description.